The invention relates to a screw compressor comprising a compressor screw housing, two screw rotors with intermeshing screw bodies arranged in the compressor screw housing and with shaft sections arranged on both sides of the screw bodies, the screw rotors being mounted by means of the shaft sections in bearing housings arranged on both sides of the compressor screw housing.
Such screw compressors are known from the prior art, and, with these, there is the problem of providing at the pressure side as tight a closure as possible between the screw bodies and the compressor screw housing, so as to prevent losses of pressure.
This problem is solved, in accordance with the invention, in a screw compressor of the kind described at the outset, by an intermediate portion of the shaft section adjoining an end of the respective screw body at the pressure side and extending as far as a bearing section being sealed off in the area of a closure wall of the compressor screw housing at the outlet side from an inside surface of an opening in the closure wall, which surrounds the intermediate portion.
The advantage of the solution according to the invention is to be seen in the fact that owing to the seal between the intermediate portion and the inside surface of the opening, the gap existing between these cannot be penetrated by a parasitic flow of compressed working mediumxe2x80x94which would travel from the volume area with compressed working medium to a volume area located opposite the outlet in close proximity to the closure wall of the compressor housing at the outlet sidexe2x80x94and which therefore does not open a bypass causing a loss of compressed working medium which should exit from the outlet.
In principle, it is possible to maintain the seal in the gap between the intermediate portion and the inside surface of the opening by a film of oil.
However, a particularly expedient solution makes provision for a seal allowing radial movements of the intermediate portion relative to the inside surface to be arranged between the intermediate portion and the inside surface.
This solution has the advantage that in contrast to a sealing with oil, which requires a substantially uniform gap, which, in addition, should be kept as small as possible, the seal allows radial movement of the intermediate portion relative to the inside surface but still ensures sufficient tightness, so that the inventive solution can be employed in standard screw compressor solutions in which a radial movement of the intermediate portion relative to the inside surface is permissible, which occurs as a result of the screw bodies being subjected to forces acting on one side.
The seal could be provided in the direction of the axis of rotation in any partial area of the intermediate portion and the inside surface. A particularly expedient solution makes provision for the seal to be arranged essentially in close proximity to an edge of the opening that faces the respective screw body, preferably in an edge area of the opening that faces the screw body. The volume existing up to the seal in the gap between the intermediate portion and the inside surface is therefore kept as small as possible from the start.
The seal preferably lies in a third of the opening adjoining the edge of the opening that faces the respective screw body.
So far, no details have been given of the way in which the seal is configured. In a particularly advantageous solution, provision is made for the seal to comprise a sealing ring which offers the possibility of sealing between the intermediate portion and the inside surface in a simple way.
Such a sealing ring could, for example, be made of elastic material, so that radial movements of the intermediate portion relative to the inside surface would result in the sealing ring being pressed to different degrees.
A particularly advantageous solution makes provision for the seal to comprise a sealing ring seated in a groove and movable radially in relation to this groove. This makes it possible to bring about the radial movements of the intermediate portion relative to the inside surface by a relative displacement of the sealing ring with respect to the groove.
Here it is particularly expedient for the groove to be arranged in the intermediate portion.
A particularly expedient solution makes provision for the groove to be arranged in the intermediate portion near the end of the respective screw body at the pressure side.
It is expedient for the distance of the groove from an end face of the respective screw body to be at most five times, even better at most three times, a width of the groove in the direction of the axis of rotation.
A further expedient solution is configured such that the intermediate portion has adjacent to the end of the respective screw body at the pressure side an indentation located opposite the edge of the opening.
Such an indentation has the advantage that contact can then be avoided between the intermediate portion and the edge of the opening when the intermediate portion moves radially relative to the inside surface of the opening.
It is particularly expedient for the groove to be arranged so as to essentially follow the indentation.
It is preferable for there to be a spacing between the groove and an end face of the respective screw body, which corresponds at most to three times the extent of the indentation in the direction of the axis of rotation, with the indentation preferably having an extent in the direction of the axis of rotation which corresponds approximately to a width of the groove.
It is even better for the spacing of the groove from the end face to be of the order of magnitude of twice the extent of the indentation in the direction of the respective axis of rotation.
A ring-shaped bead is preferably provided between the indentation and the groove to ensure proper guidance of the sealing ring.
This ring-shaped bead expediently has an extent in the direction of the axis of rotation which at most corresponds approximately to the extent of the indentation in the direction of the axis of rotation.
A particularly preferred embodiment makes provision for several sealing rings to be arranged one after the other in the direction of the axis of rotation.
Further features and advantages of the invention are the subject matter of the following description and drawings of several embodiments.